JP2007042439A - Electrolyte and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte capable of improving high temperature characteristics and to provide a battery using it. <P>SOLUTION: A positive electrode 21 and a negative electrode 22 are laminated through a separator 23. The electrolyte is impregnated in the separator 23. An ester compound expressed by R1-O-C6H4-CH=CH-COO-R2 is contained in the electrolyte. R1 is 2-4C alkyl group, 3-6C alicyclic saturated hydrocarbon group, phenyl group or these halogenation groups, and R2 is 1-4C alkyl group, 3-6C alicyclic saturated hydrocarbon group, phenyl group, these halogenation groups, trimethylsilyl group, or triethoxysilyl group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrolyte containing a solvent and a battery using the same.

  In recent years, mobile electronic devices such as mobile phones, PDAs (personal digital assistants) or notebook computers have been energetically reduced in size and weight, and as part of these efforts, Improvement of the energy density of a battery as a driving power source, particularly a secondary battery is strongly desired.

  As a secondary battery capable of obtaining a high energy density, for example, a secondary battery using lithium (Li) as an electrode reactant is known. Among these, lithium ion secondary batteries using a material capable of inserting and extracting lithium such as a carbon material in the negative electrode are widely put into practical use. In order to further increase the capacity, it has been studied to use a material capable of forming an alloy with lithium for the negative electrode.

By the way, in these secondary batteries, in order to improve battery characteristics, adding various additives to electrolyte solution is examined. For example, Patent Document 1 describes 3 ′-(trifluoromethoxy) acetophene.
Japanese Patent Application No. 2005-033444

  However, these additives cannot sufficiently suppress the decomposition reaction of the electrolytic solution at a high temperature, and further improvement has been demanded.

  The present invention has been made in view of such problems, and an object thereof is to provide an electrolyte capable of improving characteristics at high temperatures and a battery using the electrolyte.

The electrolyte according to the present invention contains a solvent containing an ester compound represented by Chemical Formula 1.
(Chemical formula 1)
_{R1-O-C 6 H 4} -CH = CH-COO-R2
(In Chemical Formula 1, R1 is an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or at least a part of these hydrogens substituted with a halogen group. R2 is an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or at least a part of these hydrogens substituted with a halogen group. Group, trimethylsilyl group, or triethoxysilyl group.)

The battery according to the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the electrolyte contains a solvent containing an ester compound represented by Chemical Formula 1.
(Chemical formula 1)
_{R1-O-C 6 H 4} -CH = CH-COO-R2
(In Chemical Formula 1, R1 is an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or at least a part of these hydrogens substituted with a halogen group. R2 is an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or at least a part of these hydrogens substituted with a halogen group. Group, trimethylsilyl group, or triethoxysilyl group.)

  According to the electrolyte of the present invention, since the ester compound represented by Chemical Formula 1 is included, for example, when used in a battery, addition polymerization is performed at a portion that is locally overcharged on the surface of the electrode. A film can be formed. Therefore, side reactions at high temperatures where local overcharge is likely to occur can be effectively suppressed, and charge / discharge efficiency can be improved.

  In particular, if the content of the ester compound with respect to the solvent is within the range of 0.08% by mass or more and 10% by mass or less, a higher effect can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, a so-called lithium ion secondary battery using lithium as an electrode reactant will be described.

[First Embodiment]
FIG. 1 shows a cross-sectional structure of a secondary battery according to the first embodiment of the present invention. This secondary battery is a so-called cylindrical type, and a wound electrode body 20 in which a belt-like positive electrode 21 and a negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. have. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are interposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. Although not shown, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

The positive electrode active material layer 21B includes a positive electrode material capable of inserting and extracting lithium, which is an electrode reactant, for example, as a positive electrode active material. As a positive electrode material capable of inserting and extracting lithium, for example, lithium-containing compounds such as lithium oxide, lithium phosphorus oxide, lithium sulfide, or an intercalation compound containing lithium are suitable, and two or more kinds are mixed. May be used. In particular, in order to increase the energy density, a lithium composite oxide or a lithium phosphorus oxide represented by the general formula Li _x MIO ₂ or Li _y MIIPO ₄ is preferable. In the formula, MI and MII represent one or more transition metals, for example, at least one of cobalt (Co), nickel, manganese (Mn), iron, aluminum, vanadium (V), and titanium (Ti). Species are preferred. The values of x and y vary depending on the charge / discharge state of the battery, and are usually values in the range of 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Specific examples of the lithium composite oxide include lithium cobalt composite oxide (LiCoO ₂ ), lithium nickel composite oxide (LiNiO ₂ ), lithium nickel cobalt composite oxide (LiNi _v Co _1-v O ₂ ; 0.7 < v <1.0), or lithium manganese composite oxide (LiMn ₂ O ₄ ) having a spinel crystal structure. Specific examples of the lithium phosphorus oxide include LiFePO ₄ or LiFe _0.5 Mn _0.5 PO ₄ .

  The positive electrode active material layer 21B also contains, for example, a conductive agent, and may further contain a binder as necessary. Examples of the conductive agent include carbon materials such as graphite, carbon black, and ketjen black, and one kind or a mixture of two or more kinds is used. In addition to the carbon material, a metal material or a conductive polymer material may be used as long as it is a conductive material. Examples of the binder include synthetic rubber such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene rubber, or a polymer material such as polyvinylidene fluoride, and one or two or more kinds are used in combination. It is done.

  The negative electrode 22 has, for example, a configuration in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer 22B includes, for example, one or more negative electrode materials capable of inserting and extracting lithium, which is an electrode reactant, as a negative electrode active material. For example, the binder similar to the positive electrode active material layer 13B may be included.

  Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon. These carbon materials are preferable because the change in crystal structure that occurs during charge / discharge is very small, a high charge / discharge capacity can be obtained, and good charge / discharge cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. The graphite may be artificial graphite or natural graphite.

  Examples of the negative electrode material capable of inserting and extracting lithium include those containing at least one of a metal element and a metalloid element capable of forming an alloy with lithium as a constituent element. This negative electrode material may be a single element or an alloy or a compound of a metal element or a metalloid element, or may have at least a part of one or more of these phases. These are preferable because a high energy density can be obtained. In particular, when used together with a carbon material, a high energy density can be obtained and excellent charge / discharge cycle characteristics can be obtained. In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of metal elements or metalloid elements capable of forming an alloy with lithium include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth ( Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium ( Hf). Among these, a group 14 metal element or metalloid element in the long-period type periodic table is preferable, and silicon or tin is particularly preferable.

Examples of the negative electrode material capable of inserting and extracting lithium further include other metal compounds or polymer materials. Examples of the other metal compounds include oxides such as iron oxide, ruthenium oxide, and molybdenum oxide, and LiN _3. Examples of the polymer material include polyacetylene.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is composed of, for example, a porous film made of a synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a porous film made of an inorganic material such as a ceramic nonwoven fabric. The porous film may be laminated.

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. The electrolytic solution includes an electrolyte salt and a solvent that dissolves the electrolyte salt.

Examples of the electrolyte salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiB (C ₆ H ₅ ) ₄ , CH _3. Examples thereof include lithium salts such as SO ₃ Li, CF ₃ SO ₃ Li, LiCl, and LiBr. As the electrolyte salt, one kind may be used alone, or two or more kinds may be mixed and used.

  Solvents include ethylene carbonate, propylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, γ-valerolactone, tetrahydrofuran, 2 -Methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate ester, butyrate ester, propionate ester, fluorobenzene, etc. Non-aqueous solvents are mentioned. As the solvent, one kind may be used alone, or two or more kinds may be mixed and used.

  Moreover, in this Embodiment, the ester compound represented by Chemical formula 1 is contained in the solvent. This ester compound has a characteristic that the addition reactivity of vinyl group is lower than that of isolated double bond such as ethylene or propylene because phenyl group, vinyl group and carbonyl group form a conjugated multiple bond. is doing. Therefore, in this secondary battery, since the ester compound is locally added and polymerized in the overcharged portion of the electrode surface to form a film, the increase in internal resistance is suppressed, and the electrolyte solution Side reactions such as decomposition, particularly side reactions at high temperatures can be effectively suppressed.

化１において、Ｒ１は、炭素数が１から４のアルキル基、炭素数が３から６の脂環式飽和炭化水素基、フェニル基、またはこれらの水素の少なくとも一部がハロゲン基で置換された基であり、Ｒ２は、炭素数が１から４のアルキル基、炭素数が３から６の脂環式飽和炭化水素基、フェニル基、これらの水素の少なくとも一部がハロゲン基で置換された基、トリメチルシリル基、またはトリエトキシシリル基である。これらの置換基を有する場合に、高い効果を得ることができるからである。

In the chemical formula 1, R1 represents an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or at least a part of these hydrogens substituted with a halogen group. R2 is an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or a group in which at least a part of these hydrogens is substituted with a halogen group , Trimethylsilyl group, or triethoxysilyl group. This is because a high effect can be obtained when these substituents are included.

  Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, and t-butyl group. . Examples of the alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms include a cyclopentyl group and a cyclohexyl group. Examples of the group in which at least a part of these hydrogens are substituted with a halogen group include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, and a pentafluoroethyl group. Among them, R1 is preferably one having a small number of carbon atoms such as a methyl group or an ethyl group. This is because when the number of carbon atoms increases, the reactivity of the vinyl group is hindered by steric hindrance.

  Further, in Chemical Formula 1, the R1O- group may be bonded to any of the 2-position, 3-position, and 4-position of the benzene ring, but is preferably bonded to the 2-position. Since carbonyl group oxygen and ether group oxygen can capture charges or radicals that promote the decomposition reaction of the electrolyte, local overcharge or side reactions of the electrolyte at the electrode can be suppressed. Because. The 1-position of the benzene ring is carbon to which a vinyl group is bonded.

  The content of the ester compound with respect to the solvent is preferably 0.08% by mass to 10% by mass, and more preferably 0.1% by mass to 9% by mass. This is because a higher effect can be obtained within this range.

  For example, the secondary battery can be manufactured as follows.

  First, the positive electrode active material layer 21B is formed on the positive electrode current collector 21A to produce the positive electrode 21, and the negative electrode active material layer 22B is formed on the negative electrode current collector 22A to produce the negative electrode 22. The positive electrode 21 and the negative electrode 22 may be formed by coating, for example, or may be formed by a gas phase method or a liquid phase method. Next, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like.

  Subsequently, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through a gasket 17. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  In the secondary battery, when charged, for example, lithium ions are released from the positive electrode active material layer 21B and inserted into the negative electrode active material layer 22B through the electrolytic solution. In addition, when discharging is performed, for example, lithium ions are released from the negative electrode active material layer 22B and inserted into the positive electrode active material layer 21B through the electrolytic solution. At that time, since the ester compound represented by Chemical Formula 1 is contained in the electrolytic solution, when local overcharge occurs in the electrode, addition polymerization is performed at that portion to form a film on the electrode. Therefore, side reactions such as decomposition of the electrolytic solution are suppressed while suppressing an increase in internal resistance.

  As described above, according to the present embodiment, since the ester compound represented by Chemical Formula 1 is included, it is possible to form a coating on a portion that is locally overcharged on the surface of the electrode. Therefore, side reactions at high temperatures where local overcharge is likely to occur can be effectively suppressed, and charge / discharge efficiency can be improved.

  In particular, if an ester compound having an R1O- group bonded to the 2-position of the benzene ring is included, a higher effect can be obtained.

  Further, if the content of the ester compound in the solvent is 0.08% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 9% by mass or less, a higher effect can be obtained. it can.

[Second Embodiment]
FIG. 3 shows the configuration of the secondary battery according to the second embodiment of the present invention. This secondary battery is a so-called laminate film type, and has a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached accommodated in a film-shaped exterior member 40.

  The positive electrode lead 31 and the negative electrode lead 32 are led out, for example, in the same direction from the inside of the exterior member 40 to the outside, and are each made of a metal material such as aluminum, copper, nickel, or stainless steel.

  The exterior member 40 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. For example, the exterior member 40 is disposed so that the polyethylene film side and the wound electrode body 30 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 40 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 4 shows an enlarged part of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is obtained by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte layer 36 interposed therebetween.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on both surfaces of a positive electrode current collector 33A, and the negative electrode 34 also has a structure in which a negative electrode active material layer 34B is provided on both surfaces of the negative electrode current collector 34A. have. The positive electrode 33 and the negative electrode 34 are disposed so that the positive electrode active material layer 33B and the negative electrode active material layer 34B face each other. The specific configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are the same as those of the positive electrode current collector 21A, the positive electrode active material layer in the first embodiment. This is the same as 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound that holds the electrolytic solution, and has a so-called gel shape. A gel electrolyte is preferable because high ion conductivity can be obtained and battery leakage can be prevented. The configuration of the electrolytic solution (that is, the solvent, the electrolyte salt, and the like) is the same as that in the first embodiment described above. Examples of the polymer material include, for example, an ether-based polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, a polymer of vinylidene fluoride such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, Or a polyacrylonitrile is mentioned, Among these, 1 type (s) or 2 or more types are mixed and used. In particular, from the viewpoint of redox stability, it is desirable to use a fluorine-based polymer compound such as a vinylidene fluoride polymer.

  For example, the secondary battery can be manufactured as follows.

  First, after forming the positive electrode 33 and the negative electrode 34 in the same manner as in the first embodiment, the electrolyte layer 36 in which the electrolytic solution is held in the polymer compound is formed on each of the positive electrode 33 and the negative electrode 34. Next, the positive electrode lead 31 is attached to the end portion of the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the end portion of the negative electrode current collector 34A. Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are stacked via the separator 35, and then wound in the longitudinal direction to form the wound electrode body 30. After that, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edge portions of the exterior members 40 are sealed and sealed by thermal fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  Further, in this secondary battery, the positive electrode 33 and the negative electrode 34 are laminated and wound via the separator 35 and sandwiched between the exterior members 40, and then the electrolytic solution and the polymer compound are opened from the opening of the exterior member 40. The electrolyte layer 36 may be formed by injecting an electrolyte composition containing a monomer as a raw material and polymerizing the monomer.

  This secondary battery operates in the same manner as in the first embodiment, and has the same effect as in the first embodiment.

  Further, specific embodiments of the present invention will be described in detail.

(Examples 1-1 to 1-15)
The laminate film type secondary battery shown in FIGS. First, lithium-cobalt composite oxide (LiCoO ₂ ) is used as a positive electrode active material, and this lithium-cobalt composite oxide, graphite as a conductive agent, and polyvinylidene fluoride as a binder are mixed to form a positive electrode composite. An agent was prepared. Next, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, and then uniformly applied to the positive electrode current collector 33A made of aluminum foil and dried, and a roll press machine The positive electrode active material layer 33B was formed by compression molding to produce the positive electrode 33.

  Further, artificial graphite was prepared as a negative electrode active material, and this negative graphite was mixed with polyvinylidene fluoride as a binder to prepare a negative electrode mixture. Next, this negative electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, and then uniformly applied to the negative electrode current collector 34A made of copper foil and dried, and a roll press machine The negative electrode active material layer 34B was formed by compression molding, and the negative electrode 34 was produced.

Subsequently, the positive electrode lead 31 was attached to the positive electrode current collector 33A, the negative electrode lead 32 was attached to the negative electrode current collector 34A, and the electrolyte layer 36 was formed on the positive electrode active material layer 33B and the negative electrode active material layer 34B. The electrolyte layer 36 is an electrolyte prepared by mixing ethylene carbonate and propylene carbonate at a mass ratio of 1: 1 and adding an ester compound represented by Chemical Formula ₁ and LiPF ₆ as an electrolyte salt. It was formed by a gel electrolyte held in a copolymer of hexafluoropropylene and vinylidene fluoride. At that time, the bonding positions of R1 and R1-O in the ester compound represented by Chemical Formula 1 were as shown in Table 1, and the content of the ester compound represented by Chemical Formula 1 in the solvent was 1% by mass. . R2 was an ethyl group. Furthermore, the content of LiPF _{6 in} the electrolytic solution was 0.6 mol / kg, and the ratio of hexafluoropropylene in the copolymer was 6.9% by mass.

  Next, the separator 35, the positive electrode 33, the separator 35, and the negative electrode 34 were stacked and wound in this order to form the wound electrode body 30, and then the wound electrode body 30 was sealed between the exterior members 40. This obtained the secondary battery of Examples 1-1 to 1-15.

  As Comparative Example 1-1 with respect to Examples 1-1 to 1-15, except that the ester compound represented by Chemical Formula 1 is not added to the electrolytic solution, the rest is the same as that of Examples 1-1 to 1-15. A secondary battery was produced. Further, as Comparative Example 1-2, a secondary battery was fabricated in the same manner as in Examples 1-1 to 1-15 except that ethyl 2- (2-naphthoxy) cinnamate was added to the electrolytic solution. . Note that ethyl 2- (2-naphthoxy) cinnamate is a compound represented by the chemical formula 1 in which R1 is a 2-naphthyl group and R2 is an ethyl group. Further, as Comparative Examples 1-3 and 1-4, 3 ′-(trifluoromethoxy) acetophenone shown in Chemical Formula 2 (1) or tri-n-butylvinyltin shown in Chemical Formula 2 (2) was used as the electrolytic solution. A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-15 except that was added. In Comparative Examples 1-2 to 1-4, the content of ethyl 2- (2-naphthoxy) cinnamate, 3 ′-(trifluoromethoxy) acetophenone or tri-n-butylvinyltin in the solvent was 1% by mass, respectively. It was.

  The fabricated secondary batteries of Examples 1-1 to 1-15 and Comparative Examples 1-1 to 1-4 were charged and discharged at 45 ° C., and the initial efficiency and high-temperature cycle characteristics were examined. Charging was performed at a constant current and constant voltage of 0.8 A and an upper limit of 4.2 V, and discharging was performed at a constant current of 0.8 A up to a final voltage of 3.0 V. The initial efficiency was obtained from the ratio of the discharge capacity to the charge capacity at the first cycle, that is, (discharge capacity at the first cycle / charge capacity at the first cycle) × 100 (%). The high-temperature cycle characteristics were determined from the ratio of the discharge capacity at the 500th cycle to the discharge capacity at the 5th cycle, that is, (discharge capacity at the 500th cycle / discharge capacity at the 5th cycle) × 100 (%). The results are shown in Table 1.

  As shown in Table 1, according to Examples 1-1 to 1-15 in which the ester compounds represented by Chemical Formula 1 having various bonding positions of R1 and R1-O were added, the ester compounds were not added. Higher values were obtained for the initial efficiency and the high-temperature cycle characteristics than Comparative Example 1-1 without Comparative Example 1-2 or Comparative Example 1-2 with other ester compound added. In Comparative Examples 1-3 and 1-4 in which other compounds were added, the initial efficiency was improved, but sufficient values were not obtained for the high-temperature cycle characteristics.

  That is, it was found that if the ester compound represented by Chemical Formula 1 is included in the electrolytic solution, the initial efficiency and cycle characteristics can be improved even under a high temperature environment.

(Examples 2-1 to 2-7)
A secondary battery was fabricated in the same manner as in Example 1-4, except that R2 in the ester compound represented by Formula 1 was changed. Specifically, in Chemical Formula 1, R1 was an ethyl group, R1-O was bonded at position 2, and R2 was as shown in Table 2.

  As Comparative Examples 2-1 and 2-2 for Examples 2-1 to 2-7, instead of the ester compound represented by Chemical Formula 1, 2-ethoxycinnamic acid or 2-ethoxy cinnamic acid (2-naphthyl) A secondary battery was fabricated in the same manner as in Examples 2-1 to 2-7 except that was added. In addition, 2-ethoxycinnamic acid is one in which R1 is an ethyl group and R2 is a hydrogen group in the chemical formula represented by Chemical Formula 1. Further, 2-ethoxycinnamic acid (2-naphthyl) is a compound in which R1 is an ethyl group and R2 is a 2-naphthyl group in the chemical formula represented by Chemical Formula 1.

  For the fabricated secondary batteries of Examples 2-1 to 2-7 and Comparative examples 2-1 and 2-2, the initial efficiency and high-temperature cycle characteristics were examined in the same manner as in Examples 1-1 to 1-15. The results are shown in Table 2 together with the results of Example 1-4 and Comparative example 1-1.

  As can be seen from Table 2, according to Examples 2-1 to 2-7 to which various ester compounds represented by Chemical Formula 1 having R2 were added, Comparative Example 2-1 using cinnamic acid, or others Higher values were obtained for the initial efficiency and the high-temperature cycle characteristics than in Comparative Example 2-2 using the above ester compound.

  That is, it was found that the initial efficiency and cycle characteristics under a high temperature environment can be improved even when other ester compounds represented by Chemical Formula 1 are used.

(Examples 3-1 to 3-10)
A secondary battery was fabricated in the same manner as in Example 1-4, except that the content of the ester compound represented by Chemical Formula 1 in the solvent was changed within the range of 0.08% by mass to 20% by mass. did. The ester compound represented by Chemical Formula 1 is ethyl 2-ethoxycinnamate (R1 and R2 are ethyl groups, and the bonding position of R1-O- is position 2).

  For the fabricated secondary batteries of Examples 3-1 to 3-10, the initial efficiency and high-temperature cycle characteristics were examined in the same manner as in Examples 1-1 to 1-15. The results are shown in Table 3 together with the results of Example 1-4 and Comparative example 1-1.

  As can be seen from Table 3, as the content of the ester compound in the solvent increased, the initial efficiency and the high-temperature cycle characteristics increased, and a tendency to decrease after showing the maximum value was observed.

  That is, it was found that the content of the ester compound represented by Chemical Formula 1 in the solvent was preferably in the range of 0.08% by mass to 10% by mass.

(Examples 4-1 to 4-5)
A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-15, except that the configuration of the negative electrode 34 was changed. At that time, the bonding positions of R1, R2 and R1-O— in the ester compound represented by Chemical Formula 1 were as shown in Table 4. In addition, content of the ester compound represented by Chemical formula 1 in a solvent is 1 mass%.

  The negative electrode 34 uses a Sn-containing material as a negative electrode active material. After mixing this Sn-containing material, artificial graphite as a conductive agent, and polyvinylidene fluoride as a binder, N-methyl-2 which is a solvent is used. -After adding pyrrolidone to form a negative electrode mixture slurry, the negative electrode current collector 34A made of copper foil is uniformly applied and dried, and compression molded with a roll press to form the negative electrode active material layer 34B Produced. As the Sn-containing material, a material made of tin, cobalt, and carbon was used.

  As Comparative Example 4-1 with respect to Examples 4-1 to 4-5, except that the ester compound represented by Chemical Formula 1 was added to the electrolytic solution, the others were the same as those of Examples 4-1 to 4-5. A secondary battery was produced. As Comparative Example 4-2, a secondary battery was fabricated in the same manner as in Examples 4-1 to 4-5, except that ethyl 2- (2-naphthoxy) cinnamate was added to the electrolytic solution. . At that time, the content of ethyl 2- (2-naphthoxy) cinnamate in the solvent was 1% by mass.

  For the fabricated secondary batteries of Examples 4-1 to 4-5 and Comparative examples 4-1 and 4-2, the initial efficiency and the high-temperature cycle characteristics were examined in the same manner as in Examples 1-1 to 1-15. The results are shown in Table 4.

  As can be seen from Table 4, according to Examples 4-1 to 4-5 to which the ester compound represented by Chemical Formula 1 was added, Comparative Example 4-1 to which no ester compound was added, or other ester compounds Higher values were obtained for the initial efficiency and the high-temperature cycle characteristics than the added Comparative Example 4-2.

  That is, even if other negative electrode active materials are used, the initial efficiency and cycle characteristics can be improved even in a high temperature environment if the electrolyte compound contains the ester compound represented by Chemical Formula 1. I understood.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the case where the electrolyte solution or the gel electrolyte in which the electrolyte solution is held in the polymer compound is used as the electrolyte has been described, but the electrolyte solution may be held in the inorganic conductor, Moreover, you may make it hold | maintain electrolyte solution in the mixture of a high molecular compound and an inorganic conductor. Examples of inorganic conductors include polycrystals of lithium nitride, lithium iodide or lithium hydroxide, a mixture of lithium iodide and dichromium trioxide, or a mixture of lithium iodide, thilium sulfide and diphosphorous subsulfide. The thing containing is mentioned.

  Moreover, although the said embodiment and Example demonstrated the case where the positive electrodes 21 and 33 and the negative electrodes 22 and 34 were wound, you may make it fold or stack | stack a positive electrode and a negative electrode. Furthermore, in the above-described embodiments and examples, a cylindrical or laminated film type secondary battery has been described. For example, other types such as an elliptical type, a polygonal type, a coin type, a button type, a square type, or a large type are described. The present invention can also be applied to a secondary battery having a shape. In addition, the present invention can be applied not only to secondary batteries but also to primary batteries.

  Furthermore, in the above-described embodiments and examples, a so-called lithium ion secondary battery, that is, a secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium has been described. The present invention can be similarly applied to the used battery. As a battery using another electrode reaction, for example, a battery in which the capacity of the negative electrode is represented by the sum of the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium, or the capacity of the negative electrode is A so-called lithium metal battery represented by a capacity component due to precipitation and dissolution of lithium can be given.

  Among these, a battery in which the capacity of the negative electrode is represented by the sum of the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium has, for example, a charge capacity of a negative electrode material capable of inserting and extracting lithium. The lithium ion secondary battery has the same configuration as the above-described lithium ion secondary battery except that lithium metal is deposited on the negative electrode during charging by being adjusted to be smaller than the charging capacity of the positive electrode. . In addition, the lithium metal battery has the same configuration as the lithium ion secondary battery described above except that the negative electrode is made of lithium metal and the like, and the precipitation and dissolution reaction of lithium is used in the negative electrode. Yes.

  Furthermore, in the above-described embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, other alkali metals such as sodium (Na) or potassium (K), magnesium or calcium (Ca), etc. The present invention can also be applied to the case of using other light metals such as alkaline earth metals or aluminum.

It is sectional drawing showing the structure of the secondary battery which concerns on the 1st Embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is a partial exploded perspective view showing the structure of the secondary battery which concerns on the 2nd Embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode current collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode current collector, 22B, 34B ... Negative electrode active material layer, 23, 35 ... Separator , 24 ... center pin, 25, 31 ... positive electrode lead, 26, 32 ... negative electrode lead, 36 ... electrolyte layer, 40 ... exterior member, 41 ... adhesion film.

Claims (6)

An electrolyte comprising a solvent containing an ester compound represented by Chemical Formula 1.
(Chemical formula 1)
_{R1-O-C 6 H 4} -CH = CH-COO-R2
(In Chemical Formula 1, R1 is an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or at least a part of these hydrogens substituted with a halogen group. R2 is an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or at least a part of these hydrogens substituted with a halogen group. Group, trimethylsilyl group, or triethoxysilyl group.)   2. The electrolyte according to claim 1, wherein a content of the ester compound with respect to the solvent is in a range of 0.08 mass% to 10 mass%.   2. The electrolyte according to claim 1, further comprising a polymer compound. A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The battery, wherein the electrolyte contains a solvent containing an ester compound represented by Chemical Formula 1.
(Chemical formula 1)
_{R1-O-C 6 H 4} -CH = CH-COO-R2
(In Chemical Formula 1, R1 is an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or at least a part of these hydrogens substituted with a halogen group. R2 is an alkyl group having 1 to 4 carbon atoms, an alicyclic saturated hydrocarbon group having 3 to 6 carbon atoms, a phenyl group, or at least a part of these hydrogens substituted with a halogen group. Group, trimethylsilyl group, or triethoxysilyl group.)   5. The battery according to claim 4, wherein a content of the ester compound with respect to the solvent is in a range of 0.08 mass% to 10 mass%. The battery according to claim 4, wherein the electrolyte further contains a polymer compound.

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